Commonly, a roofing membrane covering one or more layers of roofing insulation is attached to an underlayment, such as a metal or wooden deck, by screws and roofing washers. Galvanized steel roofing washers, polymeric roofing washers, and galvanized steel roofing washers having polymeric inserts are used.
It is known that wind and other forces produce vibrations tending to cause such a screw to work loose by causing such a roofing washer to act as a lever transmitting such forces to the screw head. As a palliative measure, it is known to form an integral assembly of such a screw and such a roofing washer, whereby it tends to be more difficult for the screw to work loose.
It is known to form such an assembly wherein the roofing washer is made from a polymeric material or has a polymeric insert, as mentioned above, and wherein the screw head is retained by being snap-fitted into a cavity of the polymeric washer or of the polymeric insert. See, e.g., Hasan U.S. Pat. No. 4,663,910 and Hasan U.S. Pat. No. 4,712,959. See, also, Dewey U.S. Pat. No. 4,380,413 and Reinwall et al. U.S. Pat. No. 4,630,984.
Also, it is known to form such an assembly wherein the roofing washer has a cavity, into which the screw head is fitted, and which is filled with a hardenable sealing compound. Such compound forms a hardened plug that prevents relative movement between the screw head and the roofing washer. See, e.g., Sandqvist U.S. Pat. No. 4,074,501. See, also, Triplett U.S. Pat. No. 4,686,808.
As a matter of related interest, it is known to form waterproof seals between the screw and the roofing washer and between the roofing washer and the roofing membrane beneath the roofing washer. See, e.g., the Sandqvist and Triplett patents noted above. See, also, Thiis-Evanson U.S. Pat. No. 4,282,050 and Francovitch U.S. Pat. No. 4,476,660.
Although various ways noted above to form an integral assembly of such screw and such a roofing washer may be generally satisfactory, there has been a need, to which this invention is addressed, for a better way to form such an assembly.